All the weather experts are predicting 2015-16 will be an El Nino winter in Northern California. The big question is will an El Nino be strong enough to relieve the present five-year drought?
An El Nino is a temporarily change in the climate of the Pacific Ocean and the region around the equator. Generally you can see the difference in both the ocean and atmosphere during a Northern Hemisphere winter. Usually the ocean surface warms up by a few degrees. At the same time, rainstorms occurring at the equator move eastward. All this activity can have a major impact on the world’s climate. Usually the wind blows strongly from east to west along the equator in the Pacific. This actually piles up water in the western part of the Pacific. In the eastern part, deeper water (which is colder than the sun-warmed surface water) gets pulled up from below to replace the water pushed west. So the normal situation is warm water in the west and cold water in the east.
However during an El Nino, the winds pushing that water around get weaker. As a result, some of the warm water piled up in the west slumps back down to the east, and not as much cold water gets pulled up from below. Both these things tend to make the water in the eastern Pacific warmer, which is one of the hallmarks of an El Nino. The warmer ocean then affects the winds by making them weaker. So if the winds are weaker, then the ocean gets warmer. This is called positive feedback and it’s what makes an El Nino grow.
There is always debate about when an El Nino will actually occur and how weak or strong it will be. In past years scientists disagreed on the conditions that lead to an El Nino. However, with modern instruments and computer models, scientists can predict an El Nino up to 12-18 months in advance with a 90-percent accuracy rate. The last major El Nino to hit Northern California occurred in 1998. That year the Bay Area received more than 12 inches of rainfall during January and nearly 15 inches in February. The total rainfall for Lakeport in 1998 was 56 inches. Normal rainfall for Lakeport is 31 inches. Clear Lake’s level rose to 11.4 feet on the Rumsey Gauge in 1998 and flooding occurred all around the lake. For example, Library Park in Lakeport had so much water that people were boating down the street past what is now the city hall.
The big question is when and if El Nino does occur, what months will it strike? Most of the experts now predict that the heaviest rainfall will occur during the months of January and February. These are the months that traditionally draw the most rain.
Even if the lake floods, the impact on the lakeshore’s residents will be minimal. In 1998 most of the land on the lake did flood but it did little damage to the homes. The lake flooding did result in all the boat ramps being closed and a number of bass tournaments were canceled. The winter months are when the majority of bass tournaments are scheduled on the lake.
The big fear about an El Nino is the damage it will do to the areas burned out during the major Valley, Rocky and Jerusalem fires of the past summer. Heavy rains could results in massive mudslides.
The good news if the lake level rises above 8 feet on the Rumsey Gauge is that the streams flowing into the lake will be running bank to bank and the hitch will have a chance to reach their spawning grounds. Bass and other game fish also will have excellent habitat because of the tules being flooded. If El Nino doesn’t materialize, then we could be headed for another year of drought.
